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454 build for towing

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Re: 454 build for towing

Postby supergass » Mon Nov 07, 2011 10:52 am

I put a early 396 cast intake on a truck I had years ago and it was originally a TBI motor with pnut port heads. It had a small cam in it too (not the TBI cam) It ran so much better with just that intake change. It had a Holley street dominator on it and when I put the cast 396 intake on it that thing would spin the tires taking off pulling the trailer. It was a half ton truck with 3.08 gears and limited slip! I would have never thought it would have made that much difference. Alan, I have a TBI motor now and I want to change the heads and intake. I have a set of open chamber heads that are ported with a 2.25 intake and the short turns done. How do you think this would work with a mild cam. Would it kill to much velocity or would it just be better fed with a small cam. Im thinking it may work. Do you think that Lunati Voodoo cam would work well?
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Re: 454 build for towing

Postby Alan Roehrich » Mon Nov 07, 2011 11:18 am

Those heads are probably too big, I'm sure the valves are. You still have to be careful since you're using it to tow, the head really needs good velocity. I was at one time sold on using 2.19" and 1.88" valves in cast iron oval port heads. Many times though, you're better off with 2.15" on the intake and the stock 1.725" exhaust, with good bowl work.

I have taken a set of 781 heads, replaced the stock valves with good stainless valves, done some bowl work, and then milled the snot out of them. You have to mill the intake when you do that, but you can get some decent compression. The biggest problem with the TBI engines is that they are the same as the old carbureted engines, the piston is usually 0.030 in the hole, so when you put a FelPro blue gasket on it, you have 0.075" compression height. But you don't really want to run a steel shim, they'll eventually rust. If it's 0.030" the hole, I think you could run a real thin Cometic and make it work okay. Again, if you do that, you're going to have to mill the head, on the intake side, too. Then you'll have to mill the end rails of the intake.

If you are running TBI, which really is not bad, you can just run an intake like the Performer RPM Q-Jet, I usually put a Trans Dapt adapter on it in place of the stock adapter.

With TBI, the practical limit for duration is around 212 @ 0.050", even though Edelbrock sells a TBI cam that is 218/228, it's big for the TBI system to "learn". Comp Cams has a nice 212/218/112 with 0.503" lift, put that in on 108 or 109. You can go bigger, but it will be harder to set up and tune, and remember, the TBI is only 650 CFM or so. You could put a set of 1.8 rockers on that.
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Re: 454 build for towing

Postby lewy-d » Tue Nov 08, 2011 8:32 am

So Alan, what would be a good target compression ration for a 454 TBI motorhome? If we are unable to come up with a set of the old 366 heads, are there any aluminum heads that could be used? Better question: what runner volume are we looking for? I'm not real big block savy. We use a 1990 flatnose motorhome to tow to & fro Bonneville. It really needs some help. we're hoping its a hyd. roller. If not It may get converted. 1 3/4" headers are ok? Get both sides together with a good merge to a 3"? 3 1/2?
Thanks for the help. I'm sure I'll have more questions.
Lewis
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Re: 454 build for towing

Postby Alan Roehrich » Tue Nov 08, 2011 9:19 am

lewy-d wrote:So Alan, what would be a good target compression ration for a 454 TBI motorhome? If we are unable to come up with a set of the old 366 heads, are there any aluminum heads that could be used? Better question: what runner volume are we looking for? I'm not real big block savy. We use a 1990 flatnose motorhome to tow to & fro Bonneville. It really needs some help. we're hoping its a hyd. roller. If not It may get converted. 1 3/4" headers are ok? Get both sides together with a good merge to a 3"? 3 1/2?
Thanks for the help. I'm sure I'll have more questions.
Lewis



What a lot of people do not know is that the 454 that comes in 30/3500 series trucks (and motorhomes) is 8:1 nominal, at best, and actually comes out around 7.5:1 or maybe 7.7:1. Combine that with a horrible head, a flat intake, and a crappy cam and you have a gutless wonder, that runs hot, cracks manifolds and gets rotten mileage.

I have never used 366 truck heads, every set I've seen has the same tiny intake port as a regular head from any truck engine, just like yours will have. I used 396/350 heads, those absolutely must have new seats in them, I use the seats for natural gas engines now. However, Edelbrock makes a head with 100cc chambers and oval ports, if you're willing to go for aluminum heads. With zero deck and a 0.042 head gasket over flat top pistons, 100cc will be pretty good. I've not seen a 1990 with a roller cam, but the good news is that many of them I've seen were two piece rear main and 4 bolt main. Makes a nice block for a 4.250 or 4.375 stroke crank. Converting to a roller valvetrain is really good. It lets you run a nice cam without worrying about it getting flat, which can be common in some big blocks

Yes, 1 3/4" headers are fine, I use Hedman headers for a 1st or second generation Camaro, those don't hang down, they clear everything nicely in a truck chassis, and they have 3" collectors. Now, for a long motorhome, a 3" single exhaust might not flow enough, a 2 1/3 might even be marginal. That's because of the heat retention as much as anything. I'm sure it is tight, but dual 3" down one side would be better, even though most companies like Flowmaster will tell you for the HP it is big enough. Again, they figure the longest they're ever talking about is a crew cab dooley. I think the heat retained in a single 2' system would drive "underhood" temperatures up, and keep the exhaust system hot. That will kill headers and mufflers, and shorten the life of good exhaust tubing. Coating the headers, and other exhaust components, like we do at NitroPlate, makes a difference there.

Finally, you have to be careful with a motorhome. Some of them do not have a great cooling system. When you make torque and HP, heat is a byproduct. You need to keep not only the coolant temp down, but also the air inlet temp, and the air around the engine as much as possible. The air inlet temp for tuning purposes, and the air around the engine in order to keep things like plug wires and other components alive longer. A well tuned engine like we're talking about is not tolerant of a dead miss when the underhood heat kills plug wires. That's another reason for exhaust coatings, the really work for that.
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Re: 454 build for towing

Postby DaveMcLain » Tue Nov 08, 2011 10:18 am

Every set of 366 heads that I've ever seen have all had the large oval port but they come with the very small truck intake valve. They also come with the truck engine exhaust valves. Speaking of which, the exhaust valve in this sort of engine is the weakest part. It's the part that fails in most high mileage truck engines, 366/427 Chevy, 391 Ford, Lima etc. A friend of mine was given a 454 Chevy that had a cracked cylinder because of an exhaust valve the lost it's head after 750,000 miles! That's right, 750,000. It was used in a truck by a local place that sells trailers. All it ever did was run down the highway picking up and delivering all sorts of different trailers. We repaired the block with a sleeve.
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Re: 454 build for towing

Postby Alan Roehrich » Tue Nov 08, 2011 10:23 am

All the 355 engines around here came from school buses. None I have seen had passenger car sized oval ports. If you can a truck head for passenger car size intake valves, you'll need to put intake seats in it.


You cannot have too good an exhaust valve in a truck engine, that is true. There is no substitute for premium valves. That's also why I mentioned that I use natural gas seats when replacing seats. It's also a good application for a sodium filled exhaust valve.
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Re: 454 build for towing

Postby DaveMcLain » Tue Nov 08, 2011 10:32 am

Gosh I built a 366 a few years ago for about an '89 Top Kick truck and it seems like it had TBI and the truck heads were not of the Peanut variety, maybe I'm mistaken. That engine did require a different intake gasket set than other big Chevy engines however because it had an extra coolant passage in the intake.
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Re: 454 build for towing

Postby Alan Roehrich » Tue Nov 08, 2011 11:38 am

DaveMcLain wrote:Gosh I built a 366 a few years ago for about an '89 Top Kick truck and it seems like it had TBI and the truck heads were not of the Peanut variety, maybe I'm mistaken. That engine did require a different intake gasket set than other big Chevy engines however because it had an extra coolant passage in the intake.


You may not be mistaken at all. Every 366 we see around here is out of a school bus, everyone else seems to buy the 427. Maybe a school bus 366 is different.
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Re: 454 build for towing

Postby Alan Roehrich » Tue Nov 08, 2011 11:39 am

Alan Roehrich wrote:All the 366 engines around here came from school buses. None I have seen had passenger car sized oval ports. If you can a truck head for passenger car size intake valves, you'll need to put intake seats in it.


You cannot have too good an exhaust valve in a truck engine, that is true. There is no substitute for premium valves. That's also why I mentioned that I use natural gas seats when replacing seats. It's also a good application for a sodium filled exhaust valve.



The bold there in the original post should read "366", not "355".
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Re: 454 build for towing

Postby lewy-d » Tue Nov 08, 2011 12:56 pm

Thanks! Ok now we're starting to lock some things in! I doubt we'll add any stroke to it. mostly 'cause I think of a greater displacement = less economy. I'd like to keep it TBI. It may wind up on megasquirt later but at least the engine won't be a dog.
What intake do you think would be good with the 212/218 cam you recommend? I think it's got some room under there for something tall. Air gap?
are 1 7/8" headers too big? dual 3" eh? common case muffler or 2 seperate mufflers? X pipe? H pipe? If we don't find the budget for alum. heads what casting are we looking for from the 396 engine?
thanks alot,
Lewis
You work at Nitroplate? I've had quite a bit of stuff coated there. The motorhome in question is Daryl Whites' of RPM. He turned me on to you guys. In fact I have a manifold that needs coating soon. You're not the owner of the GTO are you?
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Re: 454 build for towing

Postby Alan Roehrich » Tue Nov 08, 2011 1:46 pm

lewy-d wrote:Thanks! Ok now we're starting to lock some things in! I doubt we'll add any stroke to it. mostly 'cause I think of a greater displacement = less economy. I'd like to keep it TBI. It may wind up on megasquirt later but at least the engine won't be a dog.
What intake do you think would be good with the 212/218 cam you recommend? I think it's got some room under there for something tall. Air gap?
are 1 7/8" headers too big? dual 3" eh? common case muffler or 2 seperate mufflers? X pipe? H pipe? If we don't find the budget for alum. heads what casting are we looking for from the 396 engine?
thanks alot,
Lewis
You work at Nitroplate? I've had quite a bit of stuff coated there. The motorhome in question is Daryl Whites' of RPM. He turned me on to you guys. In fact I have a manifold that needs coating soon. You're not the owner of the GTO are you?


I work "with" NitroPlate. I travel to the trade shows, among a few other functions, it's mostly a volunteer sort of thing. I'm the guy who works on the race cars for the guy who is COO/CFO.

Displacement will not hurt it. I know the guys with 8.1 engines get about the same fuel economy as the guys with 7.4 engines. The key being they turn less RPM, they downshift less, and they open the throttle less.

I think once you get to a Performer RPM type intake, you're fine, an air gap style would be icing on the cake, and may help intake air temperatures, whether or not it would be enough to matter, I don't know. You'd gain more from coating it than from going from a regular intake to an air gap style.

Here's a thought. An inline two four barrel dual plane intake, with two 305 throttle bodies, or two 454 throttle bodies with 305 injectors. Plenty of airflow, better mixture distribution, and smaller injectors. I've seen it done, it works, it runs, fuel economy only changes if your foot causes it, Turbo City used to make the kit. The stock throttle body flows about 650, it is really plenty for a relatively low RPM RV/tow vehicle engine. I threw that in for the guys who might be looking at doing something more.

Yes, I think 1 7/8" headers are too big, you're not going to spin this thing 6500.

True dual exhaust is plenty, with two mufflers. I don't think there's enough to be had to worry with really high dollar mufflers and/or X/H pipes.

I personally had 720 castings on mine, but 063, 290, and 215 heads are good. Again, you probably need a full set of seats, as those are old heads, and I'd use natural gas seats. Those heads are hard to find, I have a set of 290 heads, and one each 063 and 215. I still have my 720 heads. I really don't like to sell that stuff, either, I'm a bit of a pack rat because I know how hard they are to find. The Stock and Super Stock racers use them, so they can be pricey when you do find them. You may find that by the time you buy heads, then put seats and guides in them, you'll be close to a set of bare heads from Edelbrock.
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Re: 454 build for towing

Postby coolchevy » Tue Nov 08, 2011 4:09 pm

I'll go sequential with EFIconnection hardware and self ingenuity. What do you think about the Edelbrock ProFlow X intake for that application, i can use a stock Corvette C5 throttle body on it and have electronic cruise control too?
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Re: 454 build for towing

Postby Alan Roehrich » Tue Nov 08, 2011 5:35 pm

coolchevy wrote:I'll go sequential with EFIconnection hardware and self ingenuity. What do you think about the Edelbrock ProFlow X intake for that application, i can use a stock Corvette C5 throttle body on it and have electronic cruise control too?


I think it will work well.
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Re: 454 build for towing

Postby Dodge Freak » Tue Nov 08, 2011 5:57 pm

Alan Roehrich wrote:
Here's a thought. An inline two four barrel dual plane intake, with two 305 throttle bodies, or two 454 throttle bodies with 305 injectors. Plenty of airflow, better mixture distribution, and smaller injectors. I've seen it done, it works, it runs, fuel economy only changes if your foot causes it, Turbo City used to make the kit. The stock throttle body flows about 650, it is really plenty for a relatively low RPM RV/tow vehicle engine. I threw that in for the guys who might be looking at doing something more.




Muti carbs, muti throttle bodies seem to offer the best of both power and fuel economy over any single carb. Two 500 carbs or two small throttle bodies can get better fuel economy yet flow well enough to make great power.
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Re: 454 build for towing

Postby supergass » Tue Nov 08, 2011 9:08 pm

You know I actually thought about a two four dual plane and two TBIs but I thought I probably couldnt get it to work. So Turbo City has a fix for it to work? Also will the Vortec heads work on the early Mark IV blocks?
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